Human emotions are generally considered to be characterized by brain activities. The states of the brain activities can be observed by using brain waves or the like, and various studies are currently made on the states of the brain activities by using the brain waves. Since the measurement of brain wave signals require no muscular motion, the wave signals can be easily measured compared to MEG and fMRI, and reflect the states of the brain activities. Therefore, the brain wave signals are expected to be applied to various fields. Further, it has become known that the brain waves have fractal properties, and studies have been made to elucidate the states of the brain activities by performing a fractal analysis on the brain wave signals as shown in [Non-Patent Document 1: OGO, Kiyotaka and NAKAGAWA, Masahiro, “On the Chaos and Fractal Properties in EEG Data”, Transactions of IEICE, Vol. J78-A, No. 2, pp. 161-168 (1995)], [Non-Patent Document 2: OGO, Kiyotaka and NAKAGAWA, Masahiro, “On the Chaos and Fractal Properties in EEG Data”, Electronics and Communications in Japan, Part III-Fundamentals, Vol. 78-10, pp. 27-36 (1995)], and [Non-Patent Document 3: NAKAGAWA, Masahiro, “Chaos and Fractals in Engineering”, World Scientific, Inc (1999)].
An emotion fractal dimension analysis technique has been proposed as a technique for quantitatively evaluating an emotion (“angry”, “sad”, “happy”, and “relaxed”) by characteristically using fractal dimensions obtained by separating a plurality of brain wave signals measured from a subject into a plurality of bands determined in advance, preparing a mutual correlation signal for the plurality of band-separated brain wave signals by calculating a difference between or a product of two brain wave signals selected from the plurality of band-separated brain wave signals, and performing a fractal dimension analysis on the mutual correlation signal as shown in [Non-Patent Document 4: SATO, Takahiro and NAKAGAWA, Masahiro, “Quantification of Emotions Using Fractal Dimension Analysis”, Technical Report of IEICE, HIP2002-12, pp. 13-18, 2002] and [Patent Document 1: Japanese Patent Application Publication No. 2004-194924]. Other technologies that utilize the emotion fractal dimension analysis technique include a technology for analyzing emotional information using optical topography as shown in [Non-Patent Document 5: MATSUSHITA, Shin and NAKAGAWA, Masahiro, “Emotional Information Analysis using Optical Topography”, Transactions of IEICE, Vol. J88-A, No. 8, pp. 994-1001] and a technology for application to human interfaces as shown in [Non-Patent Document 6: IIZUKA, Takuya and NAKAGAWA, Masahiro “Application to Human Interfaces Using Fractal Dimension Analysis on Brain Waves”, Technical Report of IEICE, CAS2005-42, NLP2005-54 (2005)].
Further, an emotion fractal dimension analysis technique that uses the fractal properties of brain waves as a characteristic amount has been proposed as a technique for quantitatively evaluating human emotions as shown in [Non-Patent Document 7: ITO, Naoko, KOMORI, Koki, and NAKAGAWA, Masahiro, “A Study of Spatio-Temporal Characteristics of EEG Based on the Multifractal Analysis”, Technical Report of IEICE, MBE95-70, 1995].    [Patent Document 1] Japanese Patent Application Publication No. 2004-194924    [Non-Patent Document 1] “On the Chaos and Fractal Properties in EEG Data”, Transactions of IEICE, Vol. J78-A, No. 2, pp. 161-168 (1995)    [Non-Patent Document 2] “On the Chaos and Fractal Properties in EEG Data”, Electronics and Communications in Japan, Part III-Fundamentals, Vol. 78-10, pp. 27-36 (1995)    [Non-Patent Document 3] “Chaos and Fractals in Engineering”, World Scientific, Inc (1999)    [Non-Patent Document 4] “Quantification of Emotions using Fractal Dimension Analysis”, Technical Report of IEICE, HIP2002-12, pp. 13-18, 2002    [Non-Patent Document 5] “Emotional Information Analysis using Optical Topography”, Transactions of IEICE, Vol. J88-A, No. 8, pp. 994-1001    [Non-Patent Document 6] “Application to Human Interfaces Using Fractal Dimension Analysis on Brain Waves”, Technical Report of IEICE, CAS2005-42, NLP2005-54 (2005)    [Non-Patent Document 7] ITO, Naoko, KOMORI, Koki, and NAKAGAWA, Masahiro, “A Study of Spatio-Temporal Characteristics of EEG Based on the Multifractal Analysis”, Technical Report of IEICE, MBE95-70, 1995